Bringing a Kitfox 1 back to life

[Avidventurous 32]

I never thought of using stretch wrap to isolate a mold. Jim I like your idea of using shrink wrap too. I wonder if box tape will work??? Just thinking out loud..... 

[1avidflyer 2052]

I'm  sure the box tape would work,  in one of Mike Patey's videos he did that to make a mold for duplicate parts.  He just had to spend more time smoothing up the mold where the ridges were from the layers of tape.  I should have done a mixture of the shrink wrap, and the packing tape.  JImChuk

[Good old number 29 206]

Yes, I used clear packing tape with plastic, and it works well. Because the cling wrap was prone to wrinkling, I tried using painter's film for the outlet side of the radiator baffling. It made a smoother surface, but did not release easily from the epoxy. The tape is fine. Painter's film, no. I've used 6 mil poly for other things, and it works great. It took some effort to peel the painter's film off the inside of the duct. Anyway, it all worked as intended, with a smooth outer surface, and minimal extra epoxy filling wrinkles on the inner surface. 

On the radiator inlet, two layers of 4 oz fabric made a decently strong duct. On the outlet, which I was able to wipe tighter, with no excess epoxy, due to its straight, flat sides, two layers of 4 oz. fabric was flimsy. Resin does add meaningful rigidity to some parts, though maybe not the same strength as glass. Also, the inlet had more angles, corners, and curves, with less flat, straight, surface area, allowing the walls to flex less. 

I ended up with four good layers of 4 oz on the outlet, which is light and strong. I haven't weighed it, yet, but the inlet is 6 oz.
Inlet and outlet both have 28 sq. in. openings. The inlet will be belled open at the cowl, while the outlet will have an additional duct coming off the side, for cockpit heat, with the back end open at the back, bottom edge of the cowl.

I have the upper and lower boot cowls laid up, and the front top of the cowl. Four layers of 6 oz bi-directional fabric made the same approximate rigidity and thickness as the original. 

I'm not a huge fan of epoxy, but it sure is nice to do the work inside. I grew up working with polyester resins, and still have an appreciation for how quickly it can be made to set up, and how hard its finish is, versus epoxy. I think fewer layers could have been used for my radiator shroud, with polyester. But, no way would I be doing that in the house, and not with a styrofoam form. 
There is still work to be done to the cowling, molding bumps to clear the exhaust pipes, top and bottom, fitting the airbox, which I intend to integrate into the lower cowl, shaping the front, with the air inlets, and the lower cowling.
Shown here, upside down, the radiator should have plenty of airflow, with the intake duct catching air from the inner radius of the prop. I can add volume to the inlet, on one side, if I need to increase flow, but I believe that it will be sufficient. The incoming air is pinched off a bit, with the duct tapering down to 2" in height from the radiator, at the rear. But, the opposing pressure on the outlet should also be lowest there, as it exits the opposite side, which should facilitate the even flow of cooling air through the entire surface of the radiator. 

I'll do some final smoothing, inside and out, and hit it with a coat of paint.
 

Now, back to work....

[Good old number 29 206]

A little progress on the cowling. The boot cowling fits tightly and looks good. Everything is tight in the cowling. I'm waiting for more resin to cure, for the lower cowl and exhaust bulge, before tying those parts together, then doing the final fit. 
 

I'm still working on the airbox. It's tight in the cowl. I ordered a good K&N filter that will squeeze into the narrow slot it needs to fit in. I'll set it up automotive style, with the air intake ducted to the lower box, and two hoses connecting the upper box to the carbs, above the air filter.